Hydraulic compound, for example, Portland cement clinker, blast-furnace slag and the like are ground to give various types of hydraulic powder. For instances, Portland cement is produced by calcining raw materials such as limestone, clay or iron scraps to obtain clinker, adding an appropriate amount of gypsum and grinding the mixture. In this case, in order to increase efficiency for grinding, a grinding aid such as diethylene glycol or triethanolamine is used. For a grinding process, it is desirable that hydraulic compounds are prepared efficiently as much as possible in a desired particle size. For such reasons, a grinding aid has been used for a conventional grinding process.
With respect to a grinding aid, oligomers of lower alkyleneglycol such as propyleneglycol or diethyleneglycol (for example, see JP-A 7-33487, JP-A 11-157891 and JP-A 11-322380), alkanolamines such as triethanolamine (for example, see JP-A 2002-160959), fatty acids such as stearic acid or aromatic compounds such as phenol (for example, see JP-A 5-147984), and hydroxyalkylhydrazine or tertiary butyl acetic acid and the like (for example, see JP-A 11-60298) are known. In addition, it has been also known that glycerin is used as a grinding aid (for example, see JP-A 5-147984 and JP-A 11-60298), lignin sulfonic acid salt is used in combination with glycerin (for example, see, JP-A 57-100952), and organic plant wastewater including polyhydric alcohols is used (for example, see JP-A 2005-89287). In particular, it is known that diethyleneglycol or triethanolamine has a good grinding efficiency and also can be prepared in a desired particle size at a relatively high speed.
Meanwhile, there is a problem of quality deterioration due to a decreased strength of cement, depending on conditions for production and preservation thereof. The reason for such decrease of strength includes weathering of cement that is caused by moisture released from binding water of dihydrate gypsum included in cement when the cement is stored in a silo or etc. at a high temperature, or weathering of cement caused by moisture contained in air when the cement is transferred with air. As a means to cope with such problems, it is described as an effective method in JP-A 3-187958 that silicone oil is added for grinding and manufacturing cement.